"The Rearfoot Phase … The actual shock of heel contact creates an impact of up to three times body weight."

2000 N

"The Forefoot Phase … the force exerted actually increased to between four and seven times body weight. (That means the foot of a 150 pound runner can be called upon to support a weight of a thousand pounds or more!!)"

A force is a push or a pull acting between two objects. It is a vector quantity
that has both magnitude and direction. A category of forces known as contact forces
affect us in our every day lives. The basis for the contact force is the electromagnetic
force between atoms. The contact force is also known as the normal or reaction
force. You experience these forces every day when you walk or run. As your foot
pushes against the ground, the ground pushes back, propelling you forward.

To answer the question, "What is the normal force on a human foot while
running?"we turn to of biomechanics: the study of how the body moves.

At the University of Oregon, G. A. Smith and J. E. Fewster did a study on
the variability of the ground reaction force for slow running speeds. Nine
subjects ran a series of five speeds ranging from 1.6–2.4 meters
per second. The force exerted on the ground ranged from 1,038 to 1,314 newtons
at a speed of 2.4 meters per second.

The Saucony shoe company reports that a force of up to three times body
weight can be exerted on the human foot while running. For example, a person
weighing 670 newtons (150 pounds) can experience forces of up to
seven times their body weight or 4700 newtons (1000 pounds). The
greatest force is experienced on the forefoot phase of a stride when the whole
width of the forefoot absorbs the surge of power that propels the foot off
the ground.

A similar report done by the Z-Tech shoe company states that the maximum
force can equal up to three-and-a-half times body weight. Therefore, a person
weighing 670 newtons (150 pounds) would experience a force of up
to 2300 newtons (525 pounds).

Over the course of the day, these forces can accumulate to millions of newtons (hundred or thousands of tons).